Some of you probably know that I use a BK XLS200 for subwoofer duties, the merits of which are discussed elsewhere so please don't ask about it here! I'm seriously considering throwing caution to the wind and getting another XLS200 to make a pair in my room. Having read the Harman white paper on multiple subs I'm reasonably clued up on location benefits and in the future I'll consider placing them in different parts of the room, but for now, in a room that fulfils duties as my office/bedroom/living room I don't really have space for double the footprint which leads me onto stacking a pair. Does anyone hiding in the woodwork around here have any experience of this? I've read a fair amount about it on the AV123 forums and am reasonably confident I can calibrate them to good effect (parametric equalisers and physics degrees do have benefits it would seem!). More importantly, can anyone recommend something I can put between them without damaging the finish (ie. nothing sticky like blu-tac)? I currently use doorstops as feet for my XLS200 and could get a few more of these to put between them but there are loads of other options around such as Auralex Mopads or even just a towel. At the moment I'm inclined to go with doorstops again as they're cheap and work pretty well.